基于微观结构控制的热障涂层热生长氧化物生长行为与应力状态

In order to improve the service performance at high temperature, this project is devoted to present a new route to control oxide growth behaviors in the thermal growth oxide (TGO) of thermal barrier coatings (TBCs) treated by both supersonic fine particles bombarding (SFPB) and high-current pulsed electron beams (HCPEB). We will investigate the influence of the microstructures of TGO on elements diffusion behavior and the performance as well as the service life of TBCs at high temperature by systematically characterizing the size, density and distribution of the defects structures in TGO and its adjacent zones induced by the surface treatments mentioned above. Subsequently, the relationships between microstructures and the performance of TBCs will be established. We focus on the growth and evolvement rule of TGO microstructures at different surface treatments processing. Additionally, we are planning to develop a new method to assess the interface stress of high-temperature protective coatings by establishing the relationships between residual stress and microstructures of TGO. The advantages and disadvantages compared with the conventional methods will be analyzed. HCPEB technique is used to adjust the stress states of TGO layer for improving the performance of TBCs. Based on these investigations, the effect of residual stress on the interfacial bonding propertie will be determined. This research can present some necessary theoretical and experimental storages for revealing the failure mechanism and improving the service life of TBCs at different conditions.

以热障涂层(TBCs)的热生长氧化物层(TGO)为研究载体，利用超音速微粒轰击和强流脉冲电子束复合表面处理技术控制热生长氧化物的生长和演化的新方法，改善热障涂层的高温服役性能。通过系统地表征各种表面处理条件下诱发的TGO及其附近区域晶体缺陷的类型、尺寸、密度和分布等特征及形成规律，研究TGO的微观结构状态对元素扩散行为以及热障涂层性能和寿命的影响，总结和建立微观结构与热障涂层性能之间的关系，重点研究各种表面处理条件下TGO的生长和演化规律；通过微观结构表征及测量和(或)模拟构建微观结构状态-应力之间的关系，进而建立一种评定高温防护涂层的界面应力的新方法，分析新方法与常规方法的异同点和优缺点；利用强流脉冲电子束技术调整热生长氧化物层的应力状态，并研究残余应力对界面结合性能的影响。研究结果可为揭示各种条件下热障涂层的失效机制、提高热障涂层的使用寿命提供必要的理论储备。

利用大气等离子喷涂 (APS) 的方法在基体合金表面制备双层结构热障涂层 (TBCs)，并利用强流脉冲电子束 (HCPEB) 表面改性手段分别对MCrAlY粘结层和YSZ陶瓷层表面进行轰击处理。.APS-MCrAlY表面粗糙不平，存在大量的喷涂缺陷。APS-TBCs高温氧化过程中TGO始终保持较快的生长速率，说明氧化过程中保护性氧化膜并未形成。APS-TBCs经200次热循环后表面剥落面积占总面积的34%，涂层宣告失效；150次热循环后TGO内部平均残余应力高达1.28GPa。.HCPE-MCrAlY表面重熔，形成相互连接的胞状凸起结构，内部为沿热流方向的柱状晶，且表面形成多种形态的纳米颗粒及变形结构。HCPEB处理后带来的辐照效应能够促使氧化初期连续致密的α-Al2O3膜快速形成，氧化后期氧化膜生长速度十分缓慢，TGO的厚度远小于原始样品。200次热循环后HCPEB-TBCs表面仅出现1%的边角脱落，150次热循环后TGO内部平均残余应力仅为860MPa。说明HCPEB处理粘结层后TBCs抗高温氧化和热循环性能明显提高。.HCPEB-YSZ表面形成均匀、致密的重熔层，重熔层具有表面等轴晶＋层内柱状晶的双层组织结构，且表面粗糙度随轰击次数的增加而降低，重熔层内部出现网状垂直裂纹。APS-YSZ主要由少量的单斜相m和四方相t’ 构成，而HCPEB轰击后，t’ 相的含量增加，m相的含量逐渐降低。HCPEB处理前后TGO均为双层结构，但处理涂层TGO厚度明显小于原始涂层。